Move GasMixture to shared (#27480)

* Moved GasMixture to shared

* Temp Fix for sandbox violation, idk why Array.Resize isn't working properly. It's already sandboxed.

* The most powerful webedit in history

Content.Shared/Atmos/GasMixtureStringRepresentation.cs

@@ -0,0 +1,16 @@
+namespace Content.Shared.Atmos;
+
+public readonly record struct GasMixtureStringRepresentation(float TotalMoles, float Temperature, float Pressure, Dictionary<string, float> MolesPerGas) : IFormattable
+{
+    public override string ToString()
+    {
+        return $"{Temperature}K {Pressure} kPa";
+    }
+
+    public string ToString(string? format, IFormatProvider? formatProvider)
+    {
+        return ToString();
+    }
+
+    public static implicit operator string(GasMixtureStringRepresentation rep) => rep.ToString();
+}